The present invention relates to very efficient solid compositions for washing, cleaning and bleaching as well as to a process for the manufacture of these compositions and a process for their use.
In general, solid compositions containing products of basic character, such as, for example, alkali metal silicates, carbonates, polyphosphates or hydroxides, as well as peroxy-compounds such as alkali metal percarbonates, perborates or peroxides are used for carrying out washing, cleaning and bleaching operations. The choice of the peroxidic compounds is of course restricted to the solid compounds and hitherto it has not been possible to introduce hydrogen peroxide into solid compositions. The solid peroxidic compositions are generally of low activity if the washing treatment is carried out at a relatively low temperature, or if treatments of short duration are used. To overcome this disadvantage, activators are added to these compounds. These activators make it possible to ensure that the above compounds have an acceptable efficiency even at low temperatures. The choice of the activators, however, is limited because a certain number of them have too low a melting point to enable them to be incorporated easily into solid compositions.
In addition to the peroxidic compounds, surface-active agents, which are most frequently anionic surface-active agents, such as alkylarylsulfonates with higher alkyl groups and a single aromatic nucleus, are also added to the washing, cleaning and bleaching compositions. These synthetic detergents, however, lose part of their efficiency in the presence of hard water. Accordingly, the synthetic detergents are used conjointly with one or more detergency auxiliaries, also called "builders", of which one of the principal functions is to sequester the ions responsible for the hardness of the water. The detergency auxiliaries most extensively used at the present time are sodium tripolyphosphate and also sodium nitrilotriacetate. These compounds, however, have the disadvantage of causing eutrophication of lakes and streams into which the effluents containing these compounds are discharged, because of the presence of phosphorus or nitrogen in their molecules.
To reduce the polyphosphate content of the washing, cleaning and bleaching compositions, it has been proposed either to replace the polyphosphates by builders which contain neither phosphorus nor nitrogen, or to replace at least a part of the anionic surface-active agents by non-ionic surface-active agents. Since the non-ionic surface-active agents are less affected by the hardness of the water than the anionic surface-active agents are, it is possible to reduce the phosphate content while increasing the proportion of non-ionic surface-active agent.
An non-ionic surface-active agents, there is currently used the products which owe their solubility in water to the presence of polyether chains, amine-oxide, sulfoxide or phosphine-oxide groups or alkylolamide groups, and, in general, to a substantial number of hydroxyl groups. The most extensively used non-ionic surface-active agents are alcohols with long carbon chains, ethoxylated with ethylene oxide. They generally comprise an alkyl chain of 12 to 18 carbon atoms and an average of 10 to 19 ethylene oxide units.
The main disadvantage of the compositions with a high content of non-ionic surface-active agents manifests itself, however, during their manufacture. The non-ionic surface-active agents which have a sufficiently high detergent power have an ethylene oxide content which is such that they are generally in the form of a viscous liquid or a paste at ambient temperature and are consequently unsuitable for direct addition to the dry detergent powder. Furthermore, it has been established that if too large a quantity, for example more than 5% by weight, of non-ionic surface-active agent is incorporated into the composition before spray-drying, a major problem with respect to the capacity of the drier is encountered. This problem is that these surface-active agents decompose at the temperature usually employed in spray-driers and therefore it is necessary to lower this temperature, and hence the capacity of the drier. Otherwise, dense black smoke escapes from the spray tower, causing severe pollution of the air.